Since the late 1960's, the preferred biopsy needle configuration for retrieving core tissue samples for biopsy purposes has been the so-called "Tru-Cut"-type needle assembly. This biopsy needle assembly, which is the subject of U.S. Pat. No. 3,477,423 to Griffith et al., comprises two elements, a hollow tubular cannula and a solid stylet slidably disposed within the cannula. The stylet has a sharpened forward end and a tissue receiving recess located just rearward of the forward end. The cannula has a sharpened forward edge. To retrieve a tissue specimen using the "Tru-Cut"-type biopsy needle assembly, the stylet and cannula are introduced into the patient and advanced to a point just short of the target tissue. The stylet is then manually advanced into the target tissue, and tissue prolapses into the tissue receiving recess adjacent to the forward end of the stylet. The cannula is then manually advanced, shearing off the tissue within the tissue receiving recess of the stylet and capturing the specimen. The stylet and cannula are then withdrawn together, and the tissue sample removed for analysis.
Despite its numerous advantages over then prior art biopsy needles, the "Tru-Cut"-type needle was somewhat difficult to use. Since manual advancement of the stylet occurred relatively slowly, the target tissue was sometimes pushed aside, rather than prolapsing into the tissue-receiving recess of the stylet, such that the resulting tissue specimen was not of the target tissue. Further, in the course of the physician's manually advancing the cannula, there was a tendency for the stylet to be withdrawn from the target tissue, resulting in a poor tissue specimen or even no specimen at all. These problems were addressed beginning in the early 1980's with automated, spring-actuated driving units which would be coupled to a "Tru-Cut"-type needle assembly. When the driving unit was fired, the stylet would be released, and a spring would drive the stylet forward a predetermined distance. When the stylet reached the forward extent of its travel, the cannula would instantly be released, and a spring associated with the cannula would drive it forward over the stylet, shearing off the tissue specimen and capturing it within the forward end of the cannula. This device is disclosed in PCT Application Serial No. SE83/00112.
This device, though a great improvement over a manually operated "Tru-Cut" needle, was somewhat inconvenient to operate in that a separate cocking tool had to be used to pry back slides within the driving unit to which the respective needles were coupled. This inconvenience was addressed by a device disclosed in U.S. Pat. No. 4,699,154 to Lindgren et al., which included an integral cocking slide. Actuation of the slide would simultaneously draw both needles to their cocked positions.
While both of the automated devices disclosed in PCT Application Serial No. SE83/00112 and U.S. Pat. No. 4,699,154 represented significant advances over the manually operated "Tru-Cut" needle, they were nonetheless inconvenient in certain respects. In the case of both instruments it was necessary to remove the needle assembly from the driving unit before the tissue specimen could be retrieved from the tissue receiving notch at the far end of the stylet. This problem was addressed by a device disclosed in U.S. Pat. No. 4,944,308, which had a cocking mechanism which retracted the needles sequentially, rather than simultaneously. In this manner, the cannula could be retracted without retracting the stylet, thereby affording access to the tissue receiving recess and the stylet. The cocking mechanism in the aforesaid U.S. Pat. No. 4,944,308 comprised a rotatable sleeve on the outside of the housing. Rotating the sleeve a first time cocked the cannula, and rotating the sleeve a second time cocked the stylet.
Another device which permitted independent cocking of the cannula and stylet was disclosed in U.S. Pat. No. 4,958,625, wherein the needles were cocked by slides mounted to the housing. Operating the cannula slide without operating the stylet slide would retract the cannula with respect to the stylet, thereby exposing the tissue receiving notch.
While addressing some of the inconveniences of earlier automated biopsy devices, the devices disclosed in U.S. Pat. Nos. 4,944,308 and 4,958,625 had their own disadvantages. Cocking the respective needles independently required two separate actions on the part of the physician, one for each needle. In addition, the device disclosed in U.S. Pat. No. 4,944,308 required two hands to cock the device, one hand to grasp the instrument and the other hand to rotate the sleeve. Further, the device disclosed in U.S. Pat. No. 4,958,625 comprised two slides, and it was not intuitive to the physician which slide should be cocked first. Thus the possibility existed that, in an effort to recover the tissue specimen from the tissue receiving notch, the stylet slide would be cocked first, such that the tissue sample was not exposed.
Thus, there is a need for an automated biopsy device which provides for the cannula to be cocked independently of the stylet to permit a tissue specimen to be recovered from the tissue receiving recess of the stylet, wherein the cocking order is intuitive to the physician so as to minimize the possibility that the needles are cocked in the wrong sequence.
There is a further need for an automated biopsy device which provides the advantage of being able to cock both needles simultaneously with a single action, while still permitting a tissue specimen to be recovered from the tissue receiving recess of the stylet without having to dismount the needle from the driving unit.
There is a further need for an automated biopsy device which provides the advantage of being able to cock both needles simultaneously with a single action and which permits one-handed cocking.
Another inconvenience associated with prior art automated biopsy devices concerns the location of the trigger element by which the instrument is fired. All of the aforementioned devices except one had the trigger located on the rear of the housing, a location well-suited for procedures in which the instrument would be held substantially upright. However, depending upon the style of the individual physician and the nature of the procedure being performed, there are instances in which a trigger on the side of the housing, as disclosed in U.S. Pat. No. 4,958,625, is more convenient. Neither trigger location, however, is optimal for all procedures and for all physicians.
Thus there is a need for an automated biopsy device which permits the device to be actuated from either the front or the back of the housing, depending upon the style of the individual physician and the procedure being performed.